As observed in Ref. [1]}, identifying the relevant boundaries are particularly simple in case of the one-channel dispersion relations when the polytopes in question are cyclic.We refer the reader to Ref. [1]} for the definition of this term. In case of the two-channel dispersion relations the cyclicity property is lost. However, as Ref. [1]} observed, a set of new boundaries that appear in this case involve low-spin partial waves and can be explicitly identified upon inspection. This is indeed what we observed in the examples below. To the best of our knowledge there is no proof that the list of boundaries obtained in this way is complete (and therefore that the bounds are optimal), and we do not attempt such a proof in the present work.
